Identification of Real and Artifactual Moderators of Effect Size in Meta-Analysis

This article argues that while meta-analytic studies are widely used in psychological literature, heterogeneity and the potential for confounding remain major problems in the interpretation of meta-analytic study results. The article demonstrates the use of exploratory analysis including graphical methods prior to meta-analysis, and introduces a methodology to screen for artifactual effects. These procedures are illustrated on effect size data comparing depression treatment outcome from psychotherapy versus pharmacotherapy. Results support prior findings of a nonsignificant difference in effect size between the two treatments. They also support findings that treatment type accounts for only a very small proportion of outcome variance. However, the results indicate that some previously reported covariates of depression treatment outcome may be artifactual.     

Associations between cortical thickness and general intelligence in children,adolescents and young adults

Neuroimaging research indicates that human intellectual ability is related to brain structure including the thickness of the cerebral cortex. Most studies indicate that general intelligence is positively associated with cortical thickness in areas of association cortex distributed throughout both brain hemispheres. In this study, we performed a cortical thickness mapping analysis on data from 182 healthy typically developing males and females ages 9 to 24 years to identify correlates of general intelligence (g) scores. To determine if these correlates also mediate associations of specific cognitive abilities with cortical thickness, we regressed specific cognitive test scores on g scores and analyzed the residuals with respect to cortical thickness. The effect of age on the association between cortical thickness and intelligence was examined. We found a widely distributed pattern of positive associations between cortical thickness and g scores, as derived from the first unrotated principal factor of a factor analysis of Wechsler Abbreviated Scale of Intelligence (WASI) subtest scores. After WASI specific cognitive subtest scores were regressed on g factor scores, the residual score variances did not correlate significantly with cortical thickness in the full sample with age covaried. When participants were grouped at the age median, significant positive associations of cortical thickness were obtained in the older group for g-residualized scores on Block Design (a measure of visual-motor integrative processing) while significant negative associations of cortical thickness were observed in the younger group for g-residualized Vocabulary scores. These results regarding correlates of general intelligence are concordant with the existing literature, while the findings from younger versus older subgroups have implications for future research on brain structural correlates of specific cognitive abilities, as well as the cognitive domain specificity of behavioral performance correlates of normative gray matter thinning during adolescence.     

Sales Technology Applications: Interactive Video Technology in Sales Training: A Case Study

Interactive video (IV), a new technology for training, has had a recent surge in popularity. The use of interactive video technology has been reported to reduce training costs, increase quality, and decrease the amount of time required for training. The major characteristics of this new technology are presented. A state-of-the-art application of an IV system for sales training developed at BellSouth Services is discussed. The results confirm that IV is a promising new sales training tool.     

Three dimensions of expertise

Psychologists and philosophers tend to treat expertise as a property of special individuals. These are individuals who have devoted much more time than the general population to the acquisition of their specific expertises. They are often said to pass through stages as they move toward becoming experts, for example, passing from an early stage, in which they follow self-conscious rules, to an expert stage in which skills are executed unconsciously. This approach is ‘one-dimensional’. Here, two extra dimensions are added. They are drawn from the programme known as Studies of Expertise and Experience (SEE) and its ‘Periodic Table of Expertises’. SEE, which is sociological, and/or Wittgensteinian, in inspiration, takes expertise to be the property of groups; there are ‘domains’ of expertise. Under SEE, level of expertise grows with embedding in the society of domain experts; the key is the transmission of domain-specific tacit knowledge. Thus, one extra dimension is degree of exposure to tacit knowledge. Under SEE, domains can be big or small so there can be ‘ubiquitous tacit knowledge’, such as natural-language-speaking or other elements of general social behaviour, which belong to every member of a society. The second extra dimension is, therefore, ‘esotericity’. The resulting three-dimensional ‘expertise-space’ can be explored in a number of ways which reveal the narrowness of the analysis and the mistakes that have been made under the one-dimensional model.     

Teaching Different Tasks Using Different Stimuli in a Heterogeneous Small Group

The effectiveness of a simultaneous prompting procedure was evaluated in a heterogeneous small group using different tasks and different stimuli for each student. Participants included four middle school students whose functioning levels ranged from typically developing to moderate and severe disabilities. A multiple probe design across behaviors and replicated across students was used. Observational learning maintenance, and generalization also were assessed. Results indicate that the procedure was successful in teaching all four students their targeted stimuli as well as some of the non-targeted stimuli (i.e., observational learning). Students maintained and generalized their information with a high degree of accuracy. Limitations of the study and future research implications are discussed.     

Peripheral control of drinking: gastrointestinal filling as a negative feedback signal, a theoretical and experimental analysis.

The studies described here investigated the hypothesis that the osmotic postingestional satiety signal proposed by McCleary operates through a mechanism related to gut filling rather than by osmotically induced shifts of fluid from osmoreceptors in the brain. A control theory model is presented, which was designed to make quantitatively explicit the hypothesis under question. The results showed that when mannitol, which is not absorbed from the intestine, is added to a highly palatable saccharin-glucose mixture, the amount of fluid consumed decreased in inverse proportion to the mannitol concentration. Mannitol was also shown to block fluid absorption from the intestine at a low concentration (approximately .070 M) and at higher concentrations to lead to a net flux of fluid into the intestinal lumen. It was also shown that mannitol in concentrations that reduced the intake of the palatable solution did not induce thirst when the animals were in water balance. It did induce thirst, however, when the animals were tested in a state of negative water balance. The results of these studies, considered as a whole, support the view that McCleary's osmotic postingestional satiety signal acts as an intestinal distention signal rather than by inducing thirst. The model is found to be reasonably accurate as a first approximation, and suggestions are made for improvements.